Tensioner

ABSTRACT

A tensioner comprising a base having a cylindrical portion extending axially, the cylindrical portion comprising a radially outer surface and a receiving portion that is radially inward of the radially outer surface, an eccentric arm pivotally engaged with the radially outer surface, a torsion spring disposed within the radially inward receiving portion, the torsion spring applying a biasing force to the eccentric arm, and a pulley journalled to the eccentric arm.

REFERENCE TO RELATED APPLICATIONS

This application claims priority from and is a continuation-in-part ofpending U.S. application Ser. No. 15/625,635 filed Jun. 16, 2017.

FIELD OF THE INVENTION

The invention relates to a tensioner, and more particularly, to atensioner having a torsion spring disposed within a radially inwardreceiving portion of a base cylindrical portion.

BACKGROUND OF THE INVENTION

The two most common methods synchronously driving rotating members suchas cam shafts and balance shafts from a crankshaft are timing chains andbelts. Timing chains require engine oil to operate. In comparison mosttiming belt applications require that no oil be present in the beltdrive as the presence of oil can damage the belt and inhibit itsintended purpose. Recent improvements in belts no long require that abelt be isolated from the engine oil environment.

The recent improvement of belts to operate in oil, however poses otherproblems that need to be solved. One specific problem is properlytensioning the belt drive to keep the camshaft synchronized with thecrankshaft. Should the camshaft or other synchronized driven crankshaftcomponent loose synchronization with the crankshaft catastrophic enginedamage can result.

To transmit power through the belt from the rotating crankshaft one sideof the belt is pulled around the crankshaft and is commonly referred toas the belt tight side by those skilled in the art. Conversely the otherside is referred to as the belt slack side, since the belt is being“pushed” away from the crankshaft. It is important to provide tensioningto the slack side of the belt to prevent the belt from becoming undulyslack and thus causing a loss of synchronization between the crankshaftand the components rotated by the crankshaft. This loss ofsynchronization is commonly referred to as “tooth jump” or “ratcheting”by those skilled in the art.

Known tensioners are constrained in size based on the arrangement of thecomponents. Typically a torsion spring is stacked axially with a pulleybearing. This limits the minimum height of the device, which in turnaffects the engine and belt system design.

Representative of the art is U.S. Pat. No. 9,618,098 which discloses atensioner comprising a base, a shaft connected to the base, an eccentricadjuster coaxially engaged with the shaft, an arm pivotally engaged withthe shaft, a pulley journalled to the arm, a torsion spring engagedbetween the arm and the base, the arm comprising a first receivingportion and a second receiving portion disposed axially opposite fromthe first receiving portion, a first damping member disposed between thearm and the base, the first damping member frictionally engaged with thebase and engaged with first receiving portion, a second damping memberdisposed between the arm and the eccentric adjuster having a memberengaged with the second receiving portion, and a biasing member disposedbetween the first damping member and the arm for applying a normal forceto the first damping member and to the second damping member.

What is needed is a tensioner having a torsion spring disposed within aradially inward receiving portion of a base cylindrical portion. Thepresent invention meets this need.

SUMMARY OF THE INVENTION

The primary aspect of the invention is to provide a tensioner having atorsion spring disposed within a radially inward receiving portion of abase cylindrical portion.

Other aspects of the invention will be pointed out or made obvious bythe following description of the invention and the accompanyingdrawings.

The invention comprises a tensioner comprising a base having acylindrical portion extending axially, the cylindrical portioncomprising a radially outer surface and a receiving portion that isradially inward of the radially outer surface, an eccentric armpivotally engaged with the radially outer surface, a torsion springdisposed within the radially inward receiving portion, the torsionspring applying a biasing force to the eccentric arm, and a pulleyjournalled to the eccentric arm.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate preferred embodiments of the presentinvention, and together with a description, serve to explain theprinciples of the invention.

FIG. 1 is an exploded view of the tensioner.

FIG. 2 is a top exploded view.

FIG. 3 is a perspective view of the base.

FIG. 4 is a perspective view of the eccentric arm.

FIG. 5 is a perspective view of the torsion spring.

FIG. 6 is a cross-sectional view of the tensioner.

FIG. 7 is an exploded view of an alternate embodiment.

FIG. 8 is a top view of an alternate embodiment.

FIG. 9 is a cross-sectional view of an alternate embodiment.

FIG. 10 is a side view of an alternate embodiment.

FIG. 11 is a perspective view of an alternate embodiment in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is an exploded view of the tensioner. Tensioner 100 comprises abase 10. Base 10 comprises an axially extending cylindrical portion 12having an outer surface 14. Cylindrical portion 12 further comprises anopening 11 and a receiving portion 18.

Eccentric arm 20 pivots about cylindrical portion 12. Bushing 60 isdisposed between inner surface 22 and outer surface 14. Bushing 60comprises a slot 61 which substantially aligns with opening 11 incylindrical portion 12. Pulley 40 is journalled to surface 21 on aneedle bearing 50. A needle bearing is used in an oil bath environment.Other bearings known in the art are suitable as well.

Torsion spring 30 engages and biases eccentric arm 20 toward a belt (notshown) in order to apply a belt load. End 31 projects through slot 61and opening 11 to engage eccentric arm 20 receiving portion 24. End 32engages a receiving portion 15 in base 10. Torsion spring 30 is entirelydisposed within receiving portion 18. Receiving portion 18 is a centralhollow portion of cylindrical portion 12. Torsion spring 30 is coplanarwith bearing 50, pulley 40 and eccentric arm 20. Torsion spring 30 isdisposed radially inward of pulley 40, bearing 50, bushing 60 andcylindrical portion 12. Namely, torsion spring 30, bearing 50, pulley 40and eccentric arm 20 are all concentrically arranged such that no one ofthe listed components is axially displaced, along axis A-A, from theothers.

Retaining ring 6 engages circumferential slot 16 in base 10. Retainingring 5 engages circumferential slot 23 in eccentric arm 20. Retainingring 5 retains bearing 50 on eccentric arm 20. Retaining ring 6 retainseccentric arm 20 on base 10. In the presence of oil retaining ring 5 and6 can each act as a thrust washer to transmit axial forces.

Pulley 40 is press fit on bearing 50. Fastener 4 projects throughtorsion spring 30 and hole 17 in base 10 to fix tensioner 100 to amounting surface such as an engine (not shown).

Bushing 60 comprises a dynamic coefficient of friction (COF) in therange of approximately 0.05 to approximately 0.20. A static COF ispreferably lower than the dynamic COF.

FIG. 2 is a top exploded view. Eccentric arm 20 pivots about the axisA-A, which axis is centered on cylindrical portion 12 and projectsthrough fastener 4. Eccentric arm 20 pivots about axis A-A. Pulley 40rotates about “B” which is the geometric center of eccentric arm 20. “B”is offset eccentrically from axis A-A thereby allowing eccentric pivotalmovement of eccentric arm 20 which in turn allows tensioner 100 to applya variable load to a belt (not shown).

FIG. 3 is a perspective view of the base. End receiving portion 15 isdisposed at one end of receiving portion 18 in base 10. End 32 engagesreceiving portion 15 thereby fixing end 32 and acting as a reactionpoint for the torsion spring.

FIG. 4 is a perspective view of the eccentric arm. “B” is the geometriccenter of pulley 20 and is the point about which pulley 40 rotates.Eccentric arm 20 pivots about “A” on axis A-A. Receiving portion 24engages end 31 of spring 30.

FIG. 5 is a perspective view of the torsion spring. End 31 projects intoreceiving portion 24 of eccentric arm 20. End 32 engages receivingportion 15.

FIG. 6 is a cross-sectional view of the tensioner. Torsion spring 30,bushing 60, cylindrical portion 12, eccentric arm 20, bearing 50 andpulley 40 are all concentrically arranged such that no one of the listedcomponents is axially displaced, along axis A-A, from the others. Thisfully concentric and nested arrangement minimizes the height of thetensioner allowing it to be used in very cramped applications.

FIG. 7 is an exploded view of an alternate embodiment. The componentsare the same as described herein, with the exception that the bearing 51is a plain bearing and bushing 60 is omitted. This alternate embodimentis configured to run in oil and/or is served with oil splashlubrication. Eccentric arm 20 pivots about axis A-A. Pulley 40 rotatesabout axis B-B see FIG. 4. Axis A-A is disposed away from axis B-B, andhence is not coaxial with axis A-A thereby allowing eccentric pivotalmovement of eccentric arm 20.

FIG. 8 is a top view of an alternate embodiment.

FIG. 9 is a cross-sectional view of the alternate embodiment. Torsionspring 30, eccentric arm 20 and bearing are concentrically arranged suchthat no one of the listed components is axially displaced, along axisA-A, from the others. Fluid conduit 71 in base 10 provides a path for afluid such as oil to flow from the engine oil system (not shown) tobearing 51 via fluid conduit 73, thereby lubricating the bearing. O-ring72 provides means to seal the connection to the engine oil system.

FIG. 10 is a side view of an alternate embodiment. Instead of aneccentric arm 20 and pulley 40, this alternate embodiment comprises acam 45. Cam 45 operates on the same principle as eccentric arm 20 and itoccupies the same position in the device. There is no pulley 40. Cam 45engages an elongate member 80. Elongate member 80 may comprise anysuitable low friction material known in the art. Elongate member 80 mayalso be referred to as a slide guide. A chain “C” slidingly engages asurface of slide guide 80. Pivot 81 is disposed at one end of the slideguide. Slide guide 80 pivots about pivot 81 in response to rotation ofcam 45. Due to the eccentric form of surface 46 rotation of cam 45causes slide guide 80 to pivot about 81 thereby maintaining a load onchain “C”. This embodiment is useful in an internal combustion enginetiming system by way of example.

FIG. 11 is a perspective view of the alternate embodiment in FIG. 10.Surface 46 of cam 45 engages slide guide 80.

Although forms of the invention have been described herein, it will beobvious to those skilled in the art that variations may be made in theconstruction and relation of parts and method without departing from thespirit and scope of the invention described herein.

I claim:
 1. A tensioner comprising: a base cylindrical portion having aradially outer surface and a radially inward receiving portion; aneccentric arm pivotally engaged with the radially outer surface; atorsion spring disposed within the radially inward receiving portion,the torsion spring applying a biasing force to the eccentric arm; and anelongate member engaged with the eccentric arm and disposed to pivot isresponse to a rotation of the eccentric arm.
 2. The tensioner as inclaim 1, wherein the eccentric arm and the torsion spring areconcentrically arranged such that no one of the eccentric arm or torsionspring is axially displaced along an axis A-A from the others.
 3. Thetensioner as in claim 1, wherein the eccentric arm is journalled to thebase on a bushing.
 4. The tensioner as in claim 1, wherein a pulley isjournalled to the eccentric arm on a needle bearing.